ESP32 Serial Log Monitoring

Overview

Capture serial output from ESP32 (or any microcontroller) to a file for real-time monitoring and analysis.

ESP32 Setup (Device Side)

ESP-IDF Framework

#include "esp_log.h"

static const char* TAG = "MyComponent";

void my_function() {
    ESP_LOGI(TAG, "Info message");
    ESP_LOGW(TAG, "Warning: value=%d", some_value);
    ESP_LOGE(TAG, "Error occurred");
    ESP_LOGD(TAG, "Debug details");
}

Arduino Framework

void setup() {
    Serial.begin(115200);
}

void loop() {
    Serial.println("Status: running");
    Serial.printf("Sensor: %d\n", analogRead(A0));
    delay(1000);
}

Host Side – Capture Logs

# Find serial port
PORT=$(ls /dev/cu.usbmodem* /dev/ttyUSB* /dev/ttyACM* 2>/dev/null | head -1)
echo "Found port: $PORT"

# Configure and start capture
stty -f "$PORT" 115200 raw -echo 2>/dev/null || stty -F "$PORT" 115200 raw -echo
cat "$PORT" >> /tmp/device.log &
echo "Logging to /tmp/device.log (PID: $!)"

Monitor Logs

# Real-time monitoring
tail -f /tmp/device.log

# Filter specific patterns
tail -f /tmp/device.log | grep -E "ERROR|WiFi|Button"

Search for Errors

# Find crashes and errors
grep -E "ERROR|crash|overflow|panic|assert|Backtrace" /tmp/device.log

# Find reboots (look for boot messages or uptime resets)
grep -E "boot:|rst:|Uptime: [0-9] sec" /tmp/device.log

Debug Workflow

1. Clear log before reproducing issue:

   > /tmp/device.log
   

2. Reproduce the issue

3. Analyze captured logs:

   cat /tmp/device.log
   

Common Baud Rates

Stop Logging

pkill -f "cat /dev/cu.usbmodem"
pkill -f "cat /dev/ttyUSB"

Troubleshooting

• Port not found: Check USB connection, try ls /dev/cu.* /dev/tty.*
• Permission denied: Add user to dialout group (Linux)
• Garbled output: Wrong baud rate